Time recording system



Filed Mann 21. 1947 Jan. 1, 1952 s. G. I urz l 2,580,447

TIME RECORDING SYSTEM 3 Sheets-SheeiI l I6` I .I IEI- CLOCK I9 Ie\ YI: X ,"fI? A AMPLIFIER A OsoILLAToR MODULATOR SCANNER 8 HN IO I4\ I ISN 7\ -LPF RECORDER RECORD REPROOUCER MICROPHONE 9\ i -TIME INDICATOR grwIz/wto SAMUEL G. LUTZ Gell/man Jan. l, 1952 Q G, LUTZ 2,580,447

TIME RECORDING SYSTEM Filed March 21, 1947 3 Sheets-Sheet 2 Refinance v l Posmou PosmoN /2 w23 5 mi lo 22 5 El 92|4 E192 820411] l woQ/Mo SAMUEL G. LUTZ lan. l, 1952 s G, LU-rz 2,580,447

' TIME RECORDING SYSTEM SLOW RESPONSE RELAY DETECTOR SAMQEL G. LUTz Patented Jan. 1, 1952 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 3.70 0. G. 757) 7 Claims.

This invention relates generally to recording and reproducing systems and more particularly to novel apparatus for automatically incorporating time intelligence into a recording operation and reproducing said time intelligence during; the reproducing operation.

In many sound recordings it is essential to have accurate knowledge of the time relation of the sounds recorded. For example, during a military operation in which observations are recorded from several vantage points, i't is very important to preserver the time relation between the several recordings in order to reconstruct and analyze accurately' the eli'ect oi the operation. A similar use is found in scientiil'e experiments requiring observation from separated points. It is possible to use a dead reckoning method of timing by noting the time at the beginning of the recording and calculating subsequent time by measuring the progress of the needle across the recording medium. This means is of no use if the recording process is interrupted, a likely occurrence if it is desired only to record outstanding events over a considerable period of time. Furthermore, any error in the dead reckoning increases with the extentA of the .time interval calculated.

To be practical, a device for adding' time signals to a recording operation must permit intermittent operation of the recording equipment without adjustment of the time signal source, it must prevent cumulative error, it must be sumciently compact to be readily adaptable to the facilities of the point of observation, and particularly in military uses, it must be freev ci' apparatus' too delicate to withstand the shock of gun lire, or the vibration of locomotion. The' devicei` should further provide means for reproducing the time signals separately from the other recorded intelligence to avoid any confusion that might result from their combination.

It is therefore an object of. this invention to provide an apparatus for incorporating time signals into audio recordings which may be reproduced coincident with the play back of the recordings.

It is another object of this inventionV to provide apparatus for automatically incorporating. time signals into audio recordings irrespective oi intermittent use of the recording system and not subject to cumulative error.

It is another object oi?V this invention to provide a device for automatically incorporating time signals into audio recordings andvreproducing the time signals visually and distinct from the audio signals. Y

It is another object of this invention to provide a means for generating a series of signal pulses representing time by scanning an electrically energized clockwork time source whose accuracy is independent of stability of the electrical power source.

It is another object of this invention to provide a means for visually representing four digit time signals on three rotatable drums.

Other objects and advantages of the invention will be apparent from the. following description and' accompanying drawings, in which similar characters oi reference indicate similar parts throughout the several views.

In the drawings, Fig. l is a block diagram of one embodiment of the invention.

Fig. 2 is an isometric View of a clock and photo-Y electric scanner which may be used to generate time signals;

Fig. 3A is an enlarged perspective viewy of the dials of the clock shown in Fig. 2.

Fig. 3B vis an oscillogram of the time signals produced when the clock dials are in the position shownin Fig. 3A.

Fig. 4 is a disassembled perspective view of time indicator dials, shown in al position responsive to the dial positions of Fig. 3A.

Fig. 5 is a partially cut away view of the assembled dials oi' Fig. 4 whose periphery is here shown unrolled to illustrate the markings thereon. i

Fig. 6 is a schematic diagram of a circuit suitable to operate the dials of Figs. 4 and 5.

Brieiiy, time signals are mixed with audio intelligence applied to a recording system. These time signals may be a Variable number of voltage pulses which designate time by their number. The pulses are preferably used to modulate a carrier frequency chosen near the upper limit of the band pass of the recorder system. In reproducingthel recorded sound, the time signals may separated from the audio intelligence by suitable frequency selective networks. The time signals are most conveniently produced by sca-nning, either with a contact linger or an electronic photccell, a specially constructed clock work device whose dials turn up an additional contact or line for each succeeding interval of time, the number of contacts or lines determining the number of Voltage pulses. In reproduction, the time signals may be used to operate dials marked with numbers insteadv of lines to indicate the time. The pulses themselves can be used to turn the indicating dials through step-relays. In this invention the dials are returned to zero before each new time ,Signal is applied to permit continuous reproduction of intermittent recordings. For continuous operation the time signals will occur every thirty seconds.

Referring now to the drawings in detail, a block diagram is shown in Fig. 1 of a complete system for recording and reproducing audio signals and automatic time signals. The reference source for the time signals comprises a clock I6 having mechanically driven dials which are described in detail below in reference to Fig. 3A. At thirty second intervals the clock I3 triggers a scanner I 'I as described in reference to Fig. 2.. Said scanner I'I then scans the dials of the clock I6 to produce voltage pulses described in reference to Fig. 3B which are responsive to the time indicated by the clock dials. These pulses are applied to an amplifier modulator circuit I8 to thereafter key an oscillator I9. The pulses now have the carrier frequency of the oscillator I9 and may be applied to any'standard recorder I4. Audio signals may also be applied to said recorder I 4 through a microphone I3. The audio signals and the time signals are then recorded upon closing switch 5. on any suitable recording medium such as a record I5, and may be reproduced on a suitable reproducer l. The output of the reproducer 1 may be applied directly to a loud speaker I by throwing switch 8 to the left. If this is done the .time signals will be heard simultaneously with the audio signals and the time maybe calculated by counting the number of pulses in the time signal. A more convenient method, however, is to:A separate the time signals from the laudio signals and display the former visually so that one signal will not obliterate or confuse the other. This 'can be done by choosing the carrier frequency of the oscillator I9 near the upper limit of the reproducer 7 and using a low pass filter vI I. and `high pass iilter I2 at the output of the reproducer 'I to separate the signals. The low pass filter II Will pass the audio signals tothe. speaker I0 and reject the time signals. The high pass filter I2 will reject vthe audio signals and pass the time signals to a visual time indicator Slv described below in reference to'Figs. 4, 5, and 6.

Fig. 2 illustrates an'V isometric View of the scanner I'Ia'nd the'clock IB of Fig. 1. 'Ihe clock consists of three generally cylindrical dials which may be placed in a box 20 having a viewing slot 22. in the side facingthe scanner and through which a portion of the dials is visible to the scanner I'I; These dials are turned by clockwork 2| so that their position will provide a time measure. Said clockwork 2| is preferably an electrically wound spring driven mechanism similar in'principle to that commonly used in automobile dashboard clocks. If the spring in the clockwork 2| runs down at 30 second intervals to the point where it closes a contact and energizes the winding mechanism, then these voltage impulses 30 seconds apart can also be used to trip the scanner I 1 to provide a scan and hence'a time signal every 30 seconds. The scanner can be of the photoelectric type commonly used in facsimile work. As shown here, it consists of an electric motor 23 driving a photoelectric scanning arm 28 through a suitable gear reduction such as a large gear 2l supporting the arm 28 and turned by a worm gear 26 driven by the motor 23. The pulse from the clockwork 2| starts the scanner arm 28 by energizing the release relay 25. The mechanical coupling from. the electric motor 23 to the arm 28 includ-es a sliding clutch 2t which permits this arm to stay at rest against@ vcatch 25a on the release relay 25 without shutting off vor stopping said motor 23. For a scan frequency of one scan every half minute, the scanner arm should be rotated faster than once every half minute. A new time reference is supplied each time the clockwork 2| triggers the scanner El, thus avoiding the cumulative error that would result if the scanner were left to rotate continuously. The outer end of the scanner arm 28 supports a light source and optical system 29 and a photoelectric cell 3D responsive to light from source 29 which is reliected from the dials of the clock I6. The clock dials are shown by dotted lines on their containing box 23. It is noted that the two outer dials are conical rather than cylindrical in shape and so placed with respect to the center cylindrical dial that the three together form a cylinder with a concave surface. This shape is desired because it provides a nearly uniform distance between the photocell 3Q and the dials throughout the scanning arc of the scanner.

Fig. 3A isa perspective View of the clock dials enlarged to show their relative proportions, location, and time indicia. The right dial 34 is the shape of a conical section expanding to the right. vSaid dial 34 rotates about and may be geared or directly coupled to the shaft 3i which is turned by. the clockwork 2| shown and previously described in reference to Fig. 2. The mechanical coupling of said dial and said shaft is such thatv said dial completes one revolution every five-minutes. Said dial 34, which may be called the half minuteY dial, is marked with Iii bands encirclingsame to a varying degree. The band to the Aextreme left completely encircles thel dial. f The adjacent band extends only 1% ofthe distanceabout the dial, the next adjacent band extends T815 of the distance and so on td the tenth band on the extreme right which ex- .tends onlyV one-tenth the distance about the dial. Itis important that each incomplete band should-start on a common line normal to all the bands. Thus, ,viewing the dial as it is rotated Ybrings into view through the slot 22 rst one vertical line, then 30 seconds later two vertical lines and so on. After live minutes Iii vertical'lines will appear and thirty seconds later the procedure will begin again with one vertical line. The center dial 33 is a cylindrical section whose `radius lis equal to the adjacent end of the half minute dial 34. Said center dial also rotates about the-shaft 3| and is geared either to the'shaft or vthe half minute dial so as to rotate 'one-twelfth of a revolution for each completerevolution of -the half minute dial. Said center dial is marked with twelve bands disposed in similarfashion to the ten marking the half l minute dial so that when viewed through the slot 22, rotation of the dials brings into view another vertical line on the center dial every iive minutes. lThis dial may be called the iive minute dial. Said dial makes a complete revolution in'one hour` and the procedure is then. repeated.l VThe left dial 32 is similar in size and shape to the right dial 34 but it expands to theleft.A Its smaller end is of the same size and. adjacent to the center dial 33. Said left hand dial 32 also rotates about the shaft 3| and is sc geared -to the system as to turn one-twelfth of one revolution for each revolution of the center dial 33. I Said left dial 32 is marked with twelve bands-:like those-marking the center dial 33 and inadditicn withpne wide complete band placed tothe-left of the l2narrower bands. The nar- -row bands', will appear successively in the slot 22i upon rotating the dial just as in the case of the center dialv 33 except that one hour will' elapse before the appearance of an additional line. A complete revolution of dial 32 takes 12 hours, this dial may be called the hour dial. rI'he single wide band at the left of' the narrower bands will always appear in the slot. Ii the slot' 22 is scanned by the scanning device: l'l shown in Fig. 2, av voltage pulse will be produced for each time band appearing in the' sl'ot and? the bands appearing on each dial will gilve rise` to distinct pulse groups due to the linear separation of the dials and the dial markings. Since the number of time bands appearing inthe. slot is a function of time, the numberof pulsesv in the' pulse groups is also' a function of" time;

The appearance of the single wide band at the# left of the left dial is not a function of time, however and this' band will produce a single pulse wider than the others. This puise is'V the reset pulse and is described below in reference.- to Fig. 6.

In connectionv with Fig. 3A and? also Fig. 2A it will be seen that the box 20:- and'.` the viewing' slot 22 are essential only for illustrating thezvportion ofv the dials to be scanned. and not for guiding the operation ofA the scanner.

Fig. 3B is an oscillogram of the voltage: pulsesproduced by the scanner fork the1 dial position-s' shown in'V Fig. 3A- It should be notedl thaty the photo electric cell scanning-means described may bey replaced withi au mechanical method without changing the eli-ect produced. To dothis the bands' marked on the drums might consist of conducting materialsuch as metal strips. affixed. to a nonconducting surface. Insteadet scanning these conductors with a photocell asbefore. they may be scanned.v with. a rotating, contact linger which will generate a voltageV pulse for each` conducting. strip across. which it sweeps by in-v cluding laA voltage source inseries with the con-f. tact finger and the conducting. strips.V Similarly; this result might be obtained by the use of cam operated switches.

Referring to Fig. 4 in detail.. theV dials. of the i time indicator 9.of.Fig-..1 are shown in an enlarged disassembled. perspective view.v The threeY dials'. in this iigure are responsive to the time signals produced by the clock i6, of Fig.. 1- Each dial of Fig. 4 responding to the signals of the correspondf ing dial of Fig. 3A.v The electrical and mechanicaly means for so rotating the dials.. of`Fig. 4 are.` shown by schematic diagram in Fig. 6 and the operation willi be explained below in connection therewith., The right hand dial 35V respondsv to half' minute signals and, hasrv eleven positions through which it may'be'rotated. One position is a reference position to which the dialis returned at the startU of each scanning cycle to avoidv cumulative error, theA other positions are marked with numerals and measure halfLminute intervals givingthe dia-l arange of five minutes by half-minutes. In particular, there are three columns of figures: extending aboutV the circumference of the dial35. The first columnon the rightis marked with the numeralr 1/2'" every other position after the reference position. The center column isy marked after the reference position withl once repeating. numbers', beginning with. the numeral 51 and continuing through the numeral "9 for each positionV asfollows: "53 (45" 631% 63? (K7-:gh (IT'XL (18,)1'. H8111. 9; "9:1: lett:` column is. marked similar to center:` col; umn but with the numbers ranging from; 0" through 4.'. Incineration: the righthand diariy 35.

6; is inserted within the hollowr center dial 38. as far as. theflange: 35a' separating the center and theVV right. column oi figures' on. the rightY dial.

The center dial 3B contains thirteen positions to which it.;may' be rotated, one is a reference position` and the other twelve are marked with numeralsindi'cating. ve minute intervals makingthe: range of theV dial one hour. The center dial also-has three'indicating columns but only theY left one is marked withl figures. This colf umn is marked with the' numbers 0 through 5,3 and each is repeated once making a total of. twelve; figures. The center and right column consist ofV alternate windowsl cut every other position. abouty the drum with the exception of the reference position and through which the iigures on` the: left andV center columns of the halfV minute.l dial 35 arev rendered alternately visible: as will hereinafter bev explained. A view-- ing slot 39 is'. shown in the drawing by dotted lines. This slot is cut in the box retaining the: dials so. that only onev position of each dial` is visiblek at a time. The appropriate number of: the centerN or left columns of the right dial 35- is visible; through whichever column of the center dial 36- has a window in the viewing slot; 39; It will be. noted that in any ten min-A utc period for the iirst fiveminutes the lower iivenumbers. o1A thel minute digit as represented by the left column of dial 35 mayl be viewed successively through the window in dial 36 adjacentv the first. appearance: of the ten minute digit asseen in; the left. column of center.: dial 3S. After allv the lowernumbers havebeen seen the dial 3 61 will? move-:onefposition and bring a windowv fromA its' right column into view but still display the same num-ber in its left column. The center columny off dial 35` marked with the upper five numbers ofi the minute digit will be seen for the next fiveV minutes in the viewing slot through a 'rightwindowoi the center dial 35. It should be remembered. that these dials do not revolve continuously' like; the time clock dials but return to the reference position between every new time reading..

The left dial 3.1 also has thirteen positions and moves-one position for each hour of time thereby giving it. a.y range of 142 hours. The' dial is marked with two columns of gures, theorie on the left ranging from "0 through "11 and the one on the right from 12'through 23. A sliding mask 4E placed over' the viewing slot 3S may be manual-g ly moved to cover either one of the columns to distinguisha. m. readingsl from p, m. The dials are" shown` in the positions they would assume in; response,` to the voltage pulse groups shown in Fig. 3. The wide pulse on the left returns all ,dials1 to the reference position. The first puise groupV actuatesI the: left dialv moving it two positions to either l or "13 depending upon the pesition of the slidingtmask 48; The next group of two-pulses actuantesl the center dial moving it two. positions` so that'the second 0 and a right window appear inivi'ewing'slotSil. The last; group of pulses numbering eight, actuates the right dial moving it 8 positions bringing up the numbers 3, "ii-,""and i1/21' Thel "8 is Visible through a right window of the center dial and the 1/2' isvisibleto the right ofi the center dial. The timer indication therebyv produced' is either i z G8 1/2 2r 13"'1 depending on*v the position of` the mask Referringanowfto Fig. 5i, theA threev dials er Fig.

4; arevshown. in assembledv position but unrolled 'E5-w showv the.b complete markings thereon. The

c'enter dial 36 ispartially cutaway-to illustrate the markings on 'the rportion of the right'dial l35 which lies within the center Adial 35. are so arranged that their relative positions are the same as in Fig. 4 and itwill be noted that the time 1:081/2 may be read through the viewing slot 39. The cooperative association of the indicating dials may bebetter understood by taking'this view in connection with Fig. 4. It may be noted that the indicating dials of Figs. 4 and 5 are not continuously rotated as are the clockwork dials of Fig. 3A, they are instead reset to a zero reference position before each new pulse transmission so any time lapse in the recording will not affect the accuracy of the received time transmission.

Referring to Fig. 6, there isshown a schematic diagram of the drive mechanism for the visual time indicator I5. Each of the three indicating dials, the hour dial, 31, the minute dial 36 and the half minute dial 35 are independently driven by separate step relays 49, 52 and 53. The step relays move their associated dials one step from the reference position for each pulse applied to them. Cams 55 and 56 are mechanically connected to the dials 31 and 35 respectively in such a manner, that when dials 31 and 35 are returned to reference position then the spring contacts 41 and 50 are moved to their reference positions by the small projections of cams 55 and 55. Relay 43 is a slow response relay which is responsive only to the longreset pulse. When relay 43 responds it energizes relays 44, 45, and 46. Relays 44, 45 and 46 are release relays which release the step relays 49, 52 and 53 respectively when they are energized, and thereby return dials 31, 36 and 35 respectively to their reference positions. Relays 48 and 5| are slow release relays actuating contacts 54 and 51 respectively. Said relays 48 and 5I will respond to the rst pulse of a group and remain closed throughout the group. Relay 42 is a fast acting relay,I responsive to the output of detector 4l, it responds to each individual pulse.

Detector 4| demodulates the incoming signal The dials` and applies the pulse transmission to relay 42.

The pulse transmission consists of a long reset pulse and three groups of pulses, one group to operate each dial.

The initial long pulse energizes relay 42 and the slow response relay 43, which energizes the reset release relays 44, 45, and 46 causing the indicator dials 31, 36, and 35 and the cams 55 and 56 to return to their reference position where they change switches 41 and 55 from the oi reference position to the on reference position.

The rst short pulse of group I is applied to step relay coil 4S through the slow release relay coil 48, the on reference position of contacts 41, and the contacts of relay 42. This first short pulse moves dial 31 one step thus moving cam 55 and throwing contacts 41 to the oi reference position. It also moves contacts 54 to the on position for the remaining pulses of group l by energizing the slow release relay 43. The remaining short pulses of group I complete the circuit through step relay 49, slow release relay coil 48, through the on position of contacts 54 shunting the now open contact 41, through contacts of relay 42 to ground, advancing dial 31 to its proper position.

' The slow release relay 48 will release after a denite time, :which is betweenthe first vpulse group and second pulse group, thusv setting up the circuit through contacts 54 and 41 to the second dial step relay 5I. of the second pulse group is applied to step relay coil 52 through the reference position of contacts 50, the oil reference position of contacts 41, the off position of contacts 54, and contacts 42 to ground. This pulse energizes a slow re-v of contacts 41, the off position of contacts 54 and relay contacts 42 to ground. The slow release relay 5| releases between pulse groups 2 and Sreturning contacts 51 to thefoi position.

The third pulse group energizes step relay coil *53 through the off reference position of con-Vv tact 5U, the off reference position of contacts 41, the oi position of contacts 54, andthe contacts of relay 42 to ground, thus moving dial 35 to the desired position.

Although certain specific embodiments of this invention have been herein disclosed and described, it is to be understood that they are merely illustrative of this invention and modiications may of course, be made without departing from the spirit and scope of the invention as defined in the appended claims.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. f

What is claimed is:

1. In combination, a clock operated pulse time generator periodically operative to produce a wavetrain of voltage pulses comprising a, first pulse group of one to twelve pulses representing the hours of the day, a second pulse group of one to twelve pulses representing ve minute intervals, a third pulse group of one to ten pulses representing half minutes, a time indicating means responsive to said three pulse groups and operative to indicate time in terms of hours, minutes, and half minutes.

2. In combination. a clock operated pulse time generator periodically operative to produce at half minute intervals a wavetrain of voltage pulses comprising a irst pulse group of one to twelve pulses representing the hours of the day. a second pulse group of one to twelve pulses representing five minute intervals, a third pulse group of one to ten pulses representing half -minute intervals, and a time indicating means includingthree relay operated dials, the rst said dial movable to twelve positions in response to said iirst pulse group, the second of said dials movable to twelve positions in response to said second pulse group, and the third of said dials The iirst short pulsedicating means including three relay operated dials, the rst said dial movable to twelve positions in response to said iirst pulse group, the second of said dials movable to twelve positions in response to said second pulse group, a series of twelve alternately spaced apertures formed in said second dial, and the third of said dials movable to ten positions in response to said third pulse group, said third dial being located partly within said second dial and partly viewed through said alternately spaced apertures in said second dial, and relay means operatively associated with said time indicator to return said three dials to a reference position before each series of time pulse groups in response to said single pulse, whereby the time is indicated in terms of hours, minutes, and half minutes.

4. In combination, a clock operated pulse time generator comprising three co-linear cooperatively associated rotatable cirums each having a series of spaced circumferential time marks of graduated lengths formed thereon, the time marks formed on the first drum serving to dene hour intervals of time, the time marks formed on the second dru-m serving to define ve minute intervals of time, and the time marks formed on the third drum serving to dene half minute intervals of time, clockwork means operatively associated with said drums for so rotating the same that said iirst drum makes a complete revolution every twelve hours, said second drum a complete revolution every hour and said third drum a complete revolution every five minutes, a pulse producing means periodically scanning said drums and operative responsive to the time marks formed thereon to produce three distinct pulse groups, wherein the first pulse group is indicative of the hour, the second of the iive minute intervals and the third of the half minute intervals, and a time indicating means including three relay operated dials, the rst said dials movable to twelve positions in response to said first pulse group, the second of said dials movable to twelve positions in response to said second pulse group, and the third of said dials movable to ten positions in response to said third pulse group, whereby the time is indicated in terms of hours, minutes, and half minutes.

5. A clock operated pulse time generator comprising three co-linear cooperatively associated rotatable drums each having a series of spaced circumferential time marks of graduated lengths formed thereon, the time marks formed on the iirst drum serving to define hour intervals of time, the time marks formed on the second drum serving to dene iive minute intervals of time, and the time marks -formed on the third drum serving to deiine half minute intervals of time. clockwork means operatively associated with said drum for so rotating the same that said first drum makes a complete revolution every twelve hours, said second drum a complete revolution every hour and said third drum a complete revolution every live minutes, a pulse producing means periodically scanning said drums and operative responsive to the time marks formed thereon to produce three distinct pulse groups, wherein the first pulse group is indicative of the hour, the second of the iive minute intervals and the third of the half minute intervals.

6. A clock operated pulse time generator comprising three co-linear cooperatively associated rotatable drums each having a series of spaced circumferential time marks of graduated lengths formed thereon, the iirst drum having twelve time marks thereon serving to define hour intervals of time, the second drum having twelve time marks thereon serving to denne ve minute intervals of time, and the third drum having ten time marks thereon serving to define half minute intervals i time, clockwork means operatively associated With said drums for so rotating the same that said first drum makes a complete revolution every 12 hours, said second drum a complete revolution every hour", and said third drum a complete revolution every iive minutes, a pulse producing means including a photo-electric scanning device periodically scanning said drums and operative responsive to the time marks formed thereon to produce threewdistinct pulse groups, wherein the first pulse group is indicative of the hour, the second of iive minute intervals and the third of half minute intervals.

'7. In a recording and reproducing system having means for impressing on a recording medium pulse time signals indicative of the time of day and comprising a iirst group of not more than twelve pulses indicative of the hour, a second group of not more than twelve pulses indicative of iive minute intervals, and a third group of not more than ten pulses indicative of half min-ute intervals, apparatus for reproducing the time intelligence having a iirst dial movable to twelve positions marked in hours, a step relay operatively associated with said first dial and responsive to said iirst pulse group, a second dial movable to twelve positions, a second step relay operatively associated with said second dial and responsive to said second pulse group, said dial being marked with once repeating numerals representative of ten minute intervals, a third dial movable to ten positions, a third step relay operatively associated with said third dial and responsive to said third pulse group, said third dial containing three columns of numerals, the iirst column consists of a series of once repeating numerals representative of on-e minute intervals extending from zero time minutes to ve minutes, the second col-umn consists of once repeating numerals representative of one minute ininrvals eX- tending from five minutes to ten minutes, the third column consists of half minute markings appearing adjacent alternate markings of the second column, whereby time is visibly indicated in terms of hours, minutes, and half minutes.

SAMUEL G. LUTZ.

REFERENCES CITED The following references are of record in the ie of this patent:

UNITED STATES PATENTS Number Name Date 700,454 Thrasher May 20, 1902 2,116,314 Jenkins May 3, 1938 2,141,203 Abbott Dec. 27, 1938 2,145,018 Tweedale Jan. 24, 1939 2,188,145 Frantz Jan. 23, 1940 2,271,539 Bryce Feb. 3, 1942 2,417,129 Rusch Mar. 11, 1947 

